Battery including aluminum components

ABSTRACT

A primary lithium battery can include a current collector that includes aluminum, a positive lead that includes aluminum, or both. The aluminum battery components can have high mechanical strength and low electrical resistance.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of and claims priority toU.S. Ser. No. 10/719,056, filed on Nov. 24, 2003 now U.S. Pat. No.7,459,234, which is hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to batteries including aluminum components.

BACKGROUND

Batteries are commonly used electrical energy sources. A batterycontains a negative electrode, typically called the anode, and apositive electrode, typically called the cathode. The anode contains anactive material that can be oxidized; the cathode contains or consumesan active material that can be reduced. The anode active material iscapable of reducing the cathode active material.

When a battery is used as an electrical energy source in a device,electrical contact is made to the anode and the cathode, allowingelectrons to flow through the device and permitting the respectiveoxidation and reduction reactions to occur to provide electrical power.An electrolyte in contact with the anode and the cathode contains ionsthat flow through the separator between the electrodes to maintaincharge balance throughout the battery during discharge.

SUMMARY

In general, a primary lithium battery includes a positive lead which caninclude aluminum. The positive lead is in electrical contact with thecathode of the battery. The cathode includes a current collector whichcan include aluminum.

In one aspect, a primary lithium battery includes an anode including alithium-containing anode active material, a cathode, a separator betweenthe anode and the cathode, and a positive lead including aluminum incontact with a portion of the cathode. In another aspect, a primarylithium battery includes an anode including a lithium-containing anodeactive material, a cathode including a current collector includingaluminum, a separator between the anode and the cathode, and a positivelead including aluminum in contact with the cathode. In another aspect,a method of making a primary lithium battery includes placing a cathodein a housing, and contacting the cathode with a positive lead includingaluminum.

The lithium-containing anode active material can be lithium or a lithiumalloy. The positive lead can include a 1000 series aluminum, a 2000series aluminum alloy, a 3000 series aluminum alloy, a 5000 seriesaluminum alloy, a 6000 series aluminum alloy, or a 7000 series aluminumalloy. The positive lead can include an aluminum alloy including 0-0.4%by weight of chromium, 0.01-6.8% by weight of copper, 0.05-1.3% byweight of iron, 0.1-7% by weight of magnesium, 0-2% by weight ofmanganese, 0-2% by weight of silicon, less than 0.25% by weight oftitanium, 0-2.3% by weight of nickel, and 0-8.2% by weight of zinc. Thepositive lead can include an extension directed toward the cathode. Thepositive lead can include four or more extensions directed toward thecathode. The positive lead can include six or more extensions directedtoward the cathode. The positive lead can be welded to a portion of thecathode.

The cathode can include a current collector including aluminum. Thecurrent collector can include a 1000 series aluminum, a 2000 seriesaluminum alloy, a 3000 series aluminum alloy, a 5000 series aluminumalloy, a 6000 series aluminum alloy, or a 7000 series aluminum alloy.The current collector can include an aluminum alloy including 0-0.4% byweight of chromium, 0.01-6.8% by weight of copper, 0.05-1.3% by weightof iron, 0.1-7% by weight of magnesium 0-2% by weight of manganese, 0-2%by weight of silicon, less than 0.25% by weight of titanium, 0-2.3% byweight of nickel, and 0-8.2% by weight of zinc. The cathode can includea manganese dioxide, a carbon fluoride such as carbon monofluoride,polycarbon monofluoride, graphite fluoride, or CF_(x), iron disulfide,or a vanadate.

The battery can include a nonaqueous electrolyte in contact with theanode, the cathode and the separator. The method can include placing anonaqueous electrolyte in the housing. In the method, contacting caninclude welding. The nonaqueous electrolyte can include an organicsolvent. The nonaqueous electrolyte can include a perchlorate salt. Thebattery can be a cylindrical battery. The battery can have an impedanceof less than 0.150 Ohms, or less than 0.130 Ohms. The battery can havean impedance that increases by less than 0.20 Ohms after the battery isdropped six times from a height of one meter onto a hard surface. Thehousing can be a cylindrical housing.

Primary lithium batteries including a positive lead that includesaluminum can have a lower impedance than batteries having a positivelead of a different material, for example stainless steel. Thecombination of a cathode current collector including aluminum and apositive lead including aluminum can provide greater corrosion stabilityand conductivity in a battery than the combination of a currentcollector including aluminum and a positive lead of stainless steel.Aluminum or an aluminum alloy can be less expensive than stainlesssteel.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic drawing of a battery.

FIG. 2 is a schematic drawing of a grid.

FIGS. 3A and 3B are schematic drawings of a positive lead for a battery.

FIG. 4 is a graph depicting change in impedance of batteries after adrop test.

FIG. 5 is a graph depicting battery performance after a drop test.

FIG. 6 is a graph depicting battery performance after a drop test.

DETAILED DESCRIPTION

Referring to FIG. 1, a primary lithium electrochemical cell 10 includesan anode 12 in electrical contact with a negative lead 14, a cathode 16in electrical contact with a crown 18, a separator 20 and anelectrolyte. Anode 12, cathode 16, separator 20 and the electrolyte arecontained within housing 22. The electrolyte can be a solution thatincludes a solvent system and a salt that is at least partiallydissolved in the solvent system. One end of housing 22 is closed with apositive external contact 24 and an annular insulating gasket 26 thatcan provide a gas-tight and fluid-tight seal. Crown 18 and positive lead28 connect cathode 16 to positive external contact 24. A safety valve isdisposed in the inner side of positive external contact 24 and isconfigured to decrease the pressure within battery 10 when the pressureexceeds some predetermined value. In certain circumstances, the positivelead can be circular or annular and be arranged coaxially with thecylinder, and include radial extensions in the direction of the cathode.Electrochemical cell 10 can be, for example, a cylindrical wound cell, abutton or coin cell, a prismatic cell, a rigid laminar cell or aflexible pouch, envelope or bag cell.

Anode 12 can include alkali and alkaline ear metals, such as lithium,sodium, potassium, calcium, magnesium, or alloys thereof. The anode caninclude alloys of alkali or alkaline earth metals with another metal orother metals, for example, aluminum. An anode including lithium caninclude elemental lithium or lithium alloys, or combinations thereof.

The electrolyte can be a nonaqueous electrolyte solution including asolvent and a salt. The salt can be an alkali or alkaline earth saltsuch as a lithium salt, a sodium salt, a potassium salt, a calcium salt,a magnesium salt or combinations thereof. Examples of lithium saltsinclude lithium hexafluorophosphate, lithium tetrafluoroborate, lithiumhexafluoroarsenate, lithium perchlorate, lithium iodide, lithiumbromide, lithium tetrachloroaluminate, lithiumtrifluoromethanesulfonate, LiN(CF₃SO₂)₂, and LiB(C₆H₄O₂)₂. A perchloratesalt such as lithium perchlorate can be included in the electrolyte tohelp suppress corrosion of aluminum or an aluminum alloy in the cell,for example in the current collector. The concentration of the salt inthe electrolyte solution can range from 0.01 molar to 3 molar, from 0.5molar to 1.5 molar, and in certain embodiments can be 1 molar.

The solvent can be an organic solvent. Examples of organic solventsinclude carbonates, ethers, esters, nitrites and phosphates. Examples ofcarbonates include ethylene carbonate, propylene carbonate, diethylcarbonate and ethylmethyl carbonate. Examples of ethers include diethylether, dimethyl ether, dimethoxyethane and diethoxyethane. Examples ofesters include methyl propionate, ethyl propionate, methyl butyrate andgamma-butyrolactone. Examples of nitrites include acetonitrile. Examplesof phosphates include triethylphosphate and trimethylphosphate. Theelectrolyte can be a polymeric electrolyte.

Separator 20 can be formed of any separator material used in lithiumprimary or secondary battery separators. For example, separator 20 canbe formed of polypropylene, polyethylene, polytetrafluoroethylene, apolyamide (e.g., a nylon), a polysulfone, a polyvinyl chloride, orcombinations thereof. Separator 20 can have a thickness of from about 12microns to about 75 microns and more preferably from 12 to about 37microns. Separator 20 can be cut into pieces of a similar size as anode12 and cathode 16 and placed therebetween as shown in FIG. 1. The anode,separator, and cathode can be rolled together, especially for use incylindrical cells. Anode 12, cathode 16 and separator 20 can then beplaced within housing 22 which can be made of a metal such as nickel ornickel plated steel, stainless steel, aluminum-clad stainless steelaluminum, or an aluminum alloy or a plastic such as polyvinyl chloride,polypropylene, a polysulfone, ABS or a polyamide. Housing 22 containinganode 12, cathode 16 and separator 20 can be filled with theelectrolytic solution and subsequently hermetically scaled with positiveexternal contact 24 and annular insulating gasket 26.

Cathode 16 includes a composition that includes cathode active materialthat can undergo alkali ion insertion during discharge of battery 10.The active material can be, e.g., a metal oxide, halide, orchalcogenide; alternatively, the active material can be sulfur, anorganosulfur polymer, or a conducting polymer. Specific examples includemanganese dioxide, cobalt trifluoride, molybdenum sulfide, irondisulfide, thionyl chloride, molybdenum trioxide, sulfur, (C₆H₅N)_(n),and (S₃N₂)_(n), where n is at least 2. The active material can be avanadate material, such as a vanadium pentoxide. Vanadate materials aredescribed, for example, in U.S. Pat. Nos. 6,322,928 and 5,567,548, eachof which is incorporated by reference in its entire. The active materialcan also be a carbon monofluoride, such as a compound having the formulaCF_(x), where x is 0.5 to 1.0. The cathode composition can also includea binder, for example, a polymeric binder such as PTFE, PVDF, Kraton orViton (e.g., a copolymer of vinylidene difluoride andhexafluoropropylene). The cathode composition can also include a carbonsource, such as, for example, carbon black, synthetic graphite includingexpanded graphite or non-synthetic graphite including natural graphite,an acetylenic mesophase carbon, coke, graphitized carbon nanofibers or apolyacetylenic semiconductor.

The cathode includes a current collector on which the cathode activematerial can be coated or otherwise deposited. The current collector canhave a region in contact with positive lead 28 and a second region incontact with the active material. The current collector serves toconduct electricity between the positive lead 28 and the activematerial. The current collector can be made of a material that is strongand is a good electrical conductor (i.e. has a low resistivity), forexample a metal such as stainless steel, titanium, aluminum or analuminum alloy. More specifically, the current collector advantageouslyis composed of a material having a high yield strength, e.g. greaterthan 50 MPa, a high tensile strength, e.g. greater than 100 MPa, and alow resistivity, e.g. less than 10⁻⁴ Ω·cm or less than 10⁻⁵ Ω·cm. Thealuminum or aluminum alloy current collector can cost less and have alower resistivity than one of either stainless steel or titanium.

Aluminum and aluminum alloys are generally grouped into series accordingto the other elements present in the material. For example, a 1000series aluminum is almost pure aluminum, a 2000 series aluminum alloycontains primarily aluminum and copper, a 6000 series aluminum alloycontains primarily aluminum, magnesium and silicon, and a 7000 seriesaluminum alloy contains primarily aluminum and zinc. A 1000 series, 2000series, 3000 series, 5000 series, 6000 series, or 7000 series aluminumalloy can be suitable in a current collector or a positive lead. Inparticular, the aluminum alloy can be a 2024, 6061, or a 7075 aluminumalloy. The compositions of several aluminum based materials arepresented in Table 1. Compositions of other aluminum alloys can be foundin, for example, Metals Handbook, Vol. 2—Properties and Selection:Nonferrous Alloys and Special-Purpose Materials, ASM International 10thEd. 1990, which is incorporated by reference in its entirety.

TABLE 1 Component Aluminum Aluminum Aluminum Aluminum Aluminum Aluminum(weight %) 1145 2024 3003 5052 6061 7075 Aluminum 99.45 min 93.5 98.7 97.5 98 (balance) 90 Chloride — — — — 50 ppm max — Chromium — 0.1 max —0.15-0.35  0.04-0.35% 0.18-0.28 Copper 0.05 max 3.8-4.9 0.05-0.2 0.1 max0.15-0.4% 1.2-2   Iron 0.55 max (w/ 0.5 max 0.7 max 0.4 max 0.7 max 0.5max silicon) Magnesium 0.05 max 1.2-1.8 — 2.2-2.8 0.8-1.2 2.1-2.9Manganese 0.05 max 0.3-0.9   1-1.5 0.1 max 0.15 max 0.3 max Silicon 0.55max (w/ 0.5 max 0.6 max 0.25 max 0.4-0.8 0.4 max iron) Titanium 0.03 max0.15 max — — 0.15 max 0.2 max Vanadium 0.05 max — — — — — Zinc 0.05 max0.25 max 0.1 0.1 max 0.25 max 5.1-6.1 Zirconium + Ti — — — — — 0.25 max

One form that the current collector can take is an expanded metal screenor grid, such as a non-woven expanded metal foil. Grids of stainlesssteel, aluminum or aluminum alloy are available from Dexmet Corporation(Branford, Conn.). A grid composed of aluminum or an aluminum alloy canbe lighter and less expensive, have a lower electrical resistance, andhave similar strength compared to a grid composed of stainless steel. Inorder to be processed for ultimate use in a battery, it can be importantfor a grid to have a high yield strength, such as, for a one inch widesample, greater than 2.5 lb/in (45.5 kg/m) or greater than 5 lb/in (91kg/m), and a high tensile strength, such as, for a one inch wide sample,greater than 5 lb/in (91 kg/m) or greater than 7 lb/in (127.3 kg/m), towithstand forces applied to it during cathode manufacture. Yieldstrength is the maximum pulling force that can be applied to the currentcollector before it deforms to a certain degree, for example, a 1.14inch increase in length for a sample initially 22 inches long. Tensilestrength is the maximum pulling force that can be applied to the currentcollector before it breaks.

The mechanical and electrical properties of a grid, such as hardness,yield strength, tensile strength, and resistivity, can be influenced bythe composition of the grid, the material thickness, strand width, andthe grid long dimension (LWD) and short dimension (SWD). The LWD and theSWD of the grid can reflect the machine direction of the grid. FIG. 2depicts a grid and the various dimensions of the grid. The conductivityof the grid in the LWD differs from the conductivity of the grid in theSWD. In addition, treatment of the grid such as annealing, leveling orpulling can influence its mechanical properties. Annealing, orheat-treatment, can change the hardness or temper of the material.Leveling by passing the grid between rollers can reduce the thickness ofthe grid, flatten it, and increase its temper by strain hardening. Incertain circumstances, an T3, H36 or H38 temper can be desirable.Pulling a grid involves applying a force to alter the grid dimensions,for instance by increasing the SWD. Altering the grid dimensions canalter the current path through the grid, and therefore alter theresistivity in the machine direction and/or the cross direction. Pullinga grid can decrease plasticity and increase tensile strength of thematerial. The more the grid has been pulled, the less flexible and morebrittle it can become.

In general, a cathode is made by coating a cathode material onto acurrent collector, drying and then calendering the coated currentcollector. The cathode material is prepared by mixing an active materialtogether with other components such as a binder, solvent/water, and acarbon source. The current collector can include a metal such astitanium, stainless steel, aluminum, or an aluminum alloy. The currentcollector can be an expanded metal grid.

To form the cathode material, an active material such as manganesedioxide can be combined with carbon, such as graphite and/or acetyleneblack, and mixed with small amount of water to form a mull mix. Thetotal carbon in the mull mix can be between 1% and 10%, for examplebetween 5% and 7.5%. The amount of water in the mull mix can be lessthan 5%, such as between 1% and 3%. A binder, which can be awater/polymer mixture such as a water/polyvinyl alcohol solution, can bemixed with the mull mix. The binder can include less than 10% by weightof the polymer, for example between 5% and 7.5%. The mull mix and binderare fiber blended with a polymer suspension, for examplepolytetrafluoroethylene (e.g. Teflon 30) in water, to form a cathodeslurry.

The current collector is then coated with the cathode slurry byimmersion the current collector in a tank holding the slurry. The slurrycan be mixed prior to coating. After passing through the tank, excessslurry can be removed by passing the current collector between bladesheld at a fixed gap that is determined by the desired thickness ofslurry on the current collector. The coated current collector is driedby passing it through a heated oven. Once dried, the coated currentcollector can be calendered by passing between rolls to press it to adesired thickness. The final thickness after calendering can be in therange of 10 to 30 ml's (0.254 to 0.762 mm), such as between 12 and 20mils (0.305 to 0.508 mm). Calendering can increase the strength of agrid and elongate it by 5-40%. It can be important for the currentcollector to have a high yield strength to withstand calendering. Theporosity of the cathode can be controlled by adjusting the finalthickness of the calendered cathode. After calendering, the coatedcurrent collector can be cut to a desired size. One edge of the sizedcathode can be cleared of cathode material to form a region for thecurrent collector to contact the positive lead. After edging, thecathode can be heat treated for varying periods of time in the range of30 to 180 minutes under recirculating air at temperatures between 100and 250° C. The total time can be less than 10 hours. The cathode can befurther dried under vacuum at temperatures between 100 and 250° C. priorto being transferred to a dry room for cell assembly. The amount ofcathode material on the finished current collector can be in the rangeof 80-140 mg/cm².

In a cylindrical cell, the anode and cathode are spirally wound togetherwith a portion of the cathode current collector extending axially fromone end of the roll. The portion of the current collector that extendsfrom the roll can be free of cathode active material. To connect thecurrent collector with an external contact, the exposed end of thecurrent collector can be welded to a metal tab, which is in electriccontact with an external battery contact. The grid can be rolled in themachine direction, the pulled direction, perpendicular to the machinedirection, or perpendicular to the pulled direction. The tab can bewelded to the grid to minimize the conductivity of grid and tabassembly. Alternatively, the exposed end of the current collector can bein mechanical contact (i.e. not welded) with a positive lead which is inelectric contact with an external battery contact. A cell having amechanical contact can require fewer parts and steps to manufacture thana cell with a welded contact. The mechanical contact can be moreeffective when the exposed grid is bent towards the center of the rollto create a dome or crown, with the highest point of the crown over theaxis of the roll, corresponding to the center of a cylindrical cell. Inthe crown configuration, the grid can have a denser arrangement ofstrands than in the non-shaped form. A crown can be orderly folded andthe dimensions of a crown can be precisely controlled.

The positive lead 28 can include stainless steel, aluminum, or analuminum alloy. A positive lead composed of aluminum or an aluminumalloy can be lighter and less expensive, and have a lower electricalresistance than a positive lead composed of stainless steel. Thepositive lead can be annular in shape, and can be arranged coaxiallywith the cylinder. The positive lead can also include radial extensionsin the direction of the cathode that can engage the current collector.An extension can be round (e.g. circular or oval), rectangular,triangular or another shape. The positive lead can include extensionshaving different shapes. The positive lead and the current collector arein electrical contact. It can be preferable for both the currentcollector and the positive lead to include aluminum. Electrical contactbetween the positive lead and the current collector can be achieved bymechanical contact. Alternatively, the positive lead and currentcollector can be welded together. It can be important for a mechanicalcontact to be robust, in other words, for the parts to remain inmechanical (and therefore also electrical) contact when subjected to asudden impact, such as when the battery is dropped onto a hard surface.A positive lead can have extensions projecting from a flat surface ofthe positive lead in the direction of the cathode that can mechanicallyengage the current collector, for example, a crown. The battery can bemore robust when the positive lead includes one or more extensions, thatis, the battery is less susceptible to damage when dropped on a hardsurface. The extensions can be formed by pressing a tool havingcomplementary shape into a flat blank. A positive lead can have one ormore extensions, such as four, six or more extensions. FIGS. 3A and 3Bdepict a positive lead 28 with six extensions 30. FIG. 3A shows a bottomview (i.e. a view of the surface that contacts a current collector) andFIG. 3B shows a side view of a positive lead.

The positive lead and the cathode current collector are in electricalcontact. The electrical contact can be the result of mechanical contactbetween the positive lead and current collector. Depending on thecomposition of the positive lead and current collector, the mechanicalcontact can be a stainless steel-stainless steel contact, analuminum-stainless steel contact, or an aluminum-aluminum contact. Theelectrical resistance across an aluminum-aluminum contact can be lowerthan across a stainless steel-stainless steel contact or analuminum-stainless steel contact. An aluminum-aluminum contact can bemore robust than an aluminum-stainless steel contact in a battery, asmeasured, for example, by ability of the battery to withstand a userdrop test. See Examples 3 and 4 below.

Example 1

Five metal grids were measured for tensile strength, yield strength, andresistivity in both the machine direction (MD), along which the grid ispulled, and the transverse direction (TD), perpendicular to the machinedirection. After coating and calendering, the thickness and elongationof the grids was measured. The grids were made from 1145 aluminum (Al1145), 6061 aluminum alloy (Al 6061), or 316L stainless steel (SS 316L).A grid of 6061 aluminum alloy can have a higher yield strength andtensile strength than one of 1145 aluminum alloy, as demonstrated fromthe results in Table 2.

TABLE 2 Material Al 1145 Al 6061 Al 6061 Al 6061 SS 316L Grid Initialfoil thickness (mils) 5 5 5 6 4 construction Nominal strand width (mils)10 8 8 10 7 Nominal grid LWD (mils) 100 100 100 100 100 Grid treatmentPulled None Pulled Pulled None Measured Tensile strength, MD (lb/in) 5.13.3 5.8 8.68 13.2 grid Tensile strength, TD (lb/in) 7.5 11.8 6.9 7.0983.7 properties Yield strength, MD (lb/in) 2.4 1.6 2.5 5.93 2.8 Yieldstrength, TD (lb/in) 2.0 9.1 2.4 3.57 — Resistivity, MD (mΩ/cm)* 1.422.94 1.85 — 122.9 Resistivity, TD (mΩ/cm)* 0.97 0.83 1.28 — 29.1 Avg.calendered thickness (mils) — — 16.0 15.0 14.7 Avg. calenderedelongation (%) — — 10.9 — 5.1 *Measured resistivity of a 1-cm widesample.

Example 2

Cathodes with current collectors including 6061 aluminum alloy gridswere prepared and assembled in tabbed (i.e. the current collector isconnected to the external contact by a welded tab) cells. The cathodeshad the properties listed in Table 3. The impedance was measured atambient conditions using an impedance meter set to a frequency of 1000Hz and capable of measuring voltage to an accuracy of ±1%. Closedcircuit voltage was measured immediately after discharging the cell at aconstant current of 3 A for 0.5 seconds.

TABLE 3 Material Al 6061 Al 6061 Grid construction Initial foilthickness (mils) 6 6 Strand width (mils) 10 10 LWD (mils) 100 100 Gridtreatment Pulled Leveled Measured grid Measured strand width (mils) 9.110.6 properties Measured LWD (mils) 80.3 99.6 Measured SWD (mils) 71.651.2 Initial grid thickness (mils) 18.4 14.7 Calendered thickness(mils)13.7 10.9 Cathode material loading (mils) 105.7 104.1 Measured cellAverage cell impedance (mΩ) 77.0 76.0 properties Average closed circuitvoltage (V) 2.82 2.83 Cathode porosity (%) 32.6 33.1

Example 3

The contact resistance of a 12 cm strip of 6061 aluminum alloy under a500 g weight was measured for three different metal-metal contacts. Thecontact resistance between two samples of 6061 aluminum alloy was 29±5milliOhms, an order of magnitude lower than contacts between two piecesof stainless steel, 265±28 milliOhms, or between a stainless steel and a6061 aluminum alloy, 372±64 milliOhms.

Example 4

A series of ⅔A cells were built with various combinations of currentcollector and positive lead materials. The current collectors were Al6061 (pulled or unpulled), or 316 stainless steel (SS 316). The positivelead was Al 1145. See Table 4. To determine the robustness of thecurrent collector-positive lead contact, the impedance, closed circuitvoltage, and high end camera (BC) test performance of each type of cellwas measured before and after a drop test. In the drop test a cell wasdropped six times (two times each in top, bottom, and side orientation)from a height of one meter onto a rigid concrete surface. The impedancewas measured at ambient conditions using an impedance meter set to afrequency of 1000 Hz and capable of meaning voltage to an accuracy of±1%. The measured changes in impedance for the different types of cellsafter a drop test are shown in FIG. 4. Closed circuit voltage wasmeasured immediately after discharging the cell at a constant current of3 A for 0.5 seconds. The closed circuit voltages of the different typesof cells before and after a drop test are shown in Table 4. An HEC testsimulates discharge conditions in a high end camera. Cells arerepeatedly discharged at a current of 1.8 A for 3 seconds followed by a7 second rest period. The voltage is recorded at the end of thedischarge period. The discharge-rest cycle is repeated until the cellreaches a predetermined cutoff voltage. The number of pulses beforecutoff voltages of 2.2 V and 2.0 V were reached are shown in FIGS. 5 and6, respectively. The results are summarized in Table 4. In FIGS. 4, 5,and 6, squares represent the performance of individual cells, thevertical bars represent the average, and the horizontal bars representthe standard deviation for each type of cell. The cell numbers listed inthe first column of Table 4 correspond to the numbers in FIGS. 4, 5, and6. In one case, the positive lead was modified with extensions thatprojected toward the cathode, indicated in Table 4 as “ext”. Thenotation “DB” indicates that the grid was pulled. “DDB” indicates thatthe grid was pulled more than a grid noted as “DB”.

TABLE 4 Positive lead Impedance, Impedance change CCV, CCV change Cell #Grid material material fresh (Ohms) after drop (Ohms) fresh (V) afterdrop (V) 1 Al 6061 SS 316 0.144 0.28 2.45 −0.25 2 Al 6061 DB SS 3160.206 15.9 2.29 −0.90 3 Al 6061 DB Al (no ext) 0.130 3.57 2.54 −0.92 4Al 6061 DB Al (ext) 0.127 0.06 2.56 −0.14 5 Al 6061 DDB SS 316 0.20110.7 2.25 −0.92 Control SS 316 SS 316 0.150 0.14 2.42 −0.23

Example 5

A series of ⅔A cells were built with various combinations of currentcollector and positive lead materials and subjected to a drop test, asdescribed above. The current collectors were either Al 6061 or stainlesssteel 316L. The positive lead was Al 3003, Al 5052 H36, or stainlesssteel 316L. The closed circuit voltage of the cells was measured beforeand after the drop test. See Table 5.

TABLE 5 CCV, CCV change Grid material Positive lead material fresh (V)after drop (V) Al 6061 Al 3003 2.420 0.073 Al 6061 Al 5052 H36 2.4300.042 SS 316 SS 316 2.493 0.200

A number of embodiments have been described. Nevertheless, it will beunderstood that various modifications may be made. Accordingly, otherembodiments are within the scope of the following claims.

What is claimed is:
 1. A primary lithium battery comprising: a housing;a negative electrode comprising a lithium-containing anode activematerial; a positive electrode comprising iron disulfide and a binder;an aluminum positive electrode current collector; a separator disposedbetween the negative electrode and the positive electrode and having athickness of between 12 microns and 37 microns; an electrolyte includinglithium iodide and lithium hexafluorophosphate dissolved in a solventincluding an ether; and a positive lead including aluminum in mechanicalcontact with the current collector, wherein the battery has an impedancethat increases by less than 0.20 Ohms after the battery is dropped sixtimes from a height of one meter onto a hard surface.
 2. The battery ofclaim 1, wherein the positive lead includes a 1000 series aluminum, 2000series aluminum alloy, a 3000 series aluminum alloy, a 5000 seriesaluminum alloy, a 6000 series aluminum alloy, or a 7000 series aluminumalloy.
 3. The battery of claim 1, wherein the positive lead includes a5000 series aluminum alloy.
 4. The battery of claim 1, wherein thepositive lead includes an aluminum alloy including 0-0.4% by weight ofchromium.
 5. The battery of claim 1, wherein the positive lead includesan aluminum alloy including 0.01-6.8% by weight of copper.
 6. Thebattery of claim 1, wherein the positive lead includes an aluminum alloyincluding 0.05-1.3% by weight of iron.
 7. The battery of claim 1,wherein the positive lead includes an aluminum alloy including 0.1-7% byweight of magnesium.
 8. The battery of claim 1, wherein the positivelead includes an aluminum alloy including 0-2% by weight of manganese.9. The battery of claim 1, wherein the positive lead includes analuminum alloy including 0-2% by weight of silicon.
 10. The battery ofclaim 1, wherein the positive lead includes an aluminum alloy includingless than 0.25% by weight of titanium.
 11. The battery of claim 1,wherein the positive lead includes an aluminum alloy including 0-2.3% byweight of nickel.
 12. The battery of claim 1, wherein the positive leadincludes an aluminum alloy including 0-8.2% by weight of zinc.
 13. Thebattery of claim 1, wherein the current collector includes a 1000 seriesaluminum, a 2000 series aluminum alloy, a 3000 series aluminum alloy, a5000 series aluminum alloy, a 6000 series aluminum alloy, or a 7000series aluminum alloy.
 14. The battery of claim 13, wherein the currentcollector includes a 6000 series aluminum alloy.
 15. The battery ofclaim 13, wherein the current collector includes an aluminum alloyincluding 0-0.4% by weight of chromium, 0.01-6.8% by weight of copper,0.05-1.3% by weight of iron, 0.1-7% by weight of magnesium, 0-2% byweight of manganese, 0-2% by weight of silicon, less than 0.25% byweight of titanium, 0-2.3% by weight of nickel, and 0-8.2% by weight ofzinc.
 16. The battery of claim 1, wherein the positive lead includes anextension directed toward the positive electrode.
 17. The battery ofclaim 1, wherein the positive lead includes four or more extensionsdirected toward the positive electrode.
 18. The battery of claim 1,wherein the positive lead includes six or more extensions directedtoward the positive electrode.
 19. The battery of claim 1, wherein thehousing is cylindrical.
 20. The battery of claim 1, wherein theelectrolyte includes a third lithium salt.